When light strikes a medium of higher index, it slows down, upon exiting..

[csx]

does it speed up again or maintain that reduced speed? i dont see how itd speed up again intuitively speaking...

Also, sound travels faster in solids > liq> gases...why is it that when you're under water you cant hear anything or if you speak to someone behind a door its harder to hear. Intuitively...this makes no sense to me. I understand on a molecular level why it is but in real life it doesnt seem to apply...


thanks!

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[Janus_Kinase]

Not sure if this explanation is correct but intuitively, I think the speed of light is always constant (within a medium of course) We always just use speed of light in a vacuum (c) as 3 x 10^8 and consider that the fastest light can travel because in a vacuum there is 'nothing' that can slow down or 'get in the way' of light. When light strikes a medium of higher index there is more 'stuff' that can get in the way and thus slowing down. But when light exists that medium, since speed is constant, it will return to its original speed (there is less 'stuff' to get it in the way)


I see what you mean with sound. I know for a problem, an answer was that you hear less if a wall is in the way because sound bounces off. I guess that can also apply if you are in water and sound is bouncing off of it outside.

 

[csx]

@Janus_Kinase : in regards to the sound, I think maybe possibly you are referring to dispersion. That said, if I were to scream under water and my friend on the other side of the pool were underwater, I feel like the sound would be muffled and or it would be difficult to hear if they could even hear at all. Or am I just flat wrong? intuitively this doesnt make sense to me..

 

[texan2414]

@Janus_Kinase : in regards to the sound, I think maybe possibly you are referring to dispersion. That said, if I were to scream under water and my friend on the other side of the pool were underwater, I feel like the sound would be muffled and or it would be difficult to hear if they could even hear at all. Or am I just flat wrong? intuitively this doesnt make sense to me..

You're right.
Sound waves are longitudinal waves and need a medium to propagate through. EM radiation on the other hand can propagate in vacuum.
And yes speed does change anytime it enters or exits a new medium. It is the FREQUENCY that remains constant. Change in wave velocity is generally promulgated by a change in wavelength (with the exception of Doppler shifts which are caused by frequency changes).

 

[texan2414]

Also, sound travels faster in solids > liq> gases...why is it that when you're under water you cant hear anything or if you speak to someone behind a door its harder to hear. Intuitively...this makes no sense to me. I understand on a molecular level why it is but in real life it doesnt seem to apply...


thanks!

I think here you are conflating wave speed vs intensity level (dB) of the sound wave.
I think intensity level can be influenced by many wave phenomenons (dispersion, diffraction, reflection, refraction, interference, etc.)

When you're speaking to someone behind a door, some of your own sound is being reflected off to you. The other may interfere with other particles in the air. Similarly, when the friend behind the door talks to you, he is also hearing a reflection of his own voice. Thus, very little sound actually gets transmitted through the door to both people. These effects are exacerbated underwater.